A multipath searcher is an important module of an RAKE receiver in a wideband code division multiple access (Wideband Code Division Multiple Access, WCDMA) system, and its performance directly influences performance and implementation complexity of the RAKE receiver. A function of multipath searching (or time delay estimation) is to obtain signal energy distribution characteristics at different time delay points through a matching filter, identify multipath positions having greater energy, and distribute their time amounts to different receiving paths of the RAKE receiver. The multipath searching provides information such as a multipath position and multipath strength of a wireless channel for subsequent synchronization, channel estimation, Rake reception, channel equalization, measurement, and so on.
An existing multipath searching method includes calculating steps in the following order: performing correlation and coherent accumulation on received signals and reference sequences; then performing time delay estimation; performing incoherent accumulation after a value obtained through the time delay estimation is converted into an absolute value and squared; and finally, selecting a maximum value and outputting a final time delay estimation result, where the time delay estimation specifically is:
1. Calculate correlation values of the received signals and reference signals to find a position of a global maximum value.
2. Take M discrete values in a range near the global maximum value, and perform serial estimation on each of the taken values, that is, first l−1 maximum values are multiplied by a raised cosine (Raised Cosine, RC) waveform, and subtracted from an original correlated waveform, then an lth maximum value is found, and finally L maximum value positions in each group of M groups are obtained.
3. Calculate a sum of L reconstructed waveforms, compare mean-square errors between the original waveform and the reconstructed waveforms, and select maximum value positions of the group with a minimum mean-square error as an estimated output of a multipath delay.
When multipath waveforms are reconstructed, that is, when a value of the original waveform is multiplied by an RC waveform, an ideal multipath waveform is a multiplied product of a gain of the path and the RC waveform. However, in the foregoing multipath searching method provided in the prior art, when multipath waveforms are reconstructed, a used value of the original waveform is a result of superimposing all multipath waveforms, and because influences of other multipath waveforms are included when the multipath waveforms are reconstructed, a result finally obtained has low accuracy, resulting in that multipaths with an interval less than one chip cannot be distinguished, and weak multipaths are difficult to be detected.